1. Technical Field
This application relates to a system for providing a codebook spectral envelope for bandwidth extension of a signal.
2. Related Art
Signals transmitted via an analog or digital signal path may be limited by the bandwidth of that signal path. The restricted bandwidth may result in a transmitted signal that differs from the original signal. When the signal is an acoustic speech signal for a telephone connection, the required sampling rate of the connection may result in a maximum bandwidth for the signal. The limited signal bandwidth may reduce the speech and audio qualities of the original acoustic signal. In one example, the limited bandwidth may result in a lack of high frequencies for a speech signal that may reduce the intelligibility of the speech and/or result in missing low frequency components that may degrade speech quality.
A bandwidth may be increased by using broadband or wideband digital coding and decoding. The coding/decoding may require the transmitter and the receiver to support the corresponding coding/decoding, which may require standard coding. Alternatively, bandwidth extension may be used upon receiving a transmission so that the existing connection may remain bandwidth limited. The missing frequency components of the original bandwidth limited signal may be estimated and added to the signal.